Method for improving UV radiation stability of photosensitive sunscreen filters

ABSTRACT

The invention relates to a process for improving the stability with respect to UV radiation of a photosensitive sunscreen agent, comprising the incorporation of said screening agent in a material prepared by the sol-gel route from at least one silicon alkoxide and from at least one surfactant. It is also targeted at a photostable material which comprises the combination of a photosensitive sunscreen agent and of a photostabilizing material prepared by the sol-gel route including at least one silicon alkoxide and at least one nonionic surfactant and at a cosmetic and/or dermatological composition comprising, in a cosmetically and/or dermatologically acceptable vehicle, an effective amount of a photostable material. This cosmetic and/or dermatological composition is intended mainly for protecting the skin and/or keratinous substances against ultraviolet radiation.

CROSS REFERENCE TO RELATED APPLICATIONS

This is a U.S. national phase of International Patent Application No.PCT/FR00/02688, filed Sep. 28, 2000, which claims priority to FrenchPatent Application No. 99/12320, filed Oct. 1, 1999.

The present invention relates to a process for improving the stabilitywith respect to UV radiation of a sunscreen agent which is sensitive toUV radiation. It also relates to a photostable material and to acosmetic and/or dermatological composition comprising such a material.

It is known that light radiation with wavelengths of between 280 nm and400 nm makes possible browning of the human epidermis and that rays withwavelengths of between 280 nm and 320 nm, known under the name of UV-Bradiation, result in erythemas and cutaneous burns which can be harmfulto the development of natural tanning; this UV-B radiation therefore hasto be screened out.

It is also known that UV-A rays with wavelengths of between 320 and 400nm, which result in browning of the skin, are capable of bringing abouta detrimental change in the latter, in particular in the case ofsensitive skin or of skin continually exposed to solar radiation. UV-Arays are more penetrating than UV-B rays and result in particular in aloss of elasticity of the skin and the appearance of wrinkles, leadingto premature aging. They promote the triggering of the erythemalreaction or enhance this reaction in some subjects and can even be thecause of phototoxic or photoallergic reactions. It is thereforedesirable also to screen out UV-A radiation.

Thus, with the aim of providing protection of the skin and keratinoussubstances against UV radiation, use is generally made of antisuncompositions comprising screening agents which are active in the UV-Aregion and screening agents which are active in the UV-B region.

From this perspective, a well known and particularly advantageous familyof screening agents which are active in the UV-A region is composed ofdibenzoylmethane derivatives and in particular4-t-butyl-4′-methoxydibenzoylmethane, sold by Hoffmann-Laroche under thename <<Parsol® 1789”. Likewise, a particularly advantageous family ofscreening agents which are active in the UV-B region is currentlycomposed of cinnamic acid derivatives and in particular 2-ethylhexylp-cinnamate, sold by Hoffmann-Laroche under the name <<Parsol® MCX”.

In point of fact, sunscreen agents such as Parsol® 1789 and Parsol® MCXexhibit a major problem of sensitivity to UV radiation. This is becauseit is found that dibenzoylmethane derivatives are products which arerelatively sensitive to ultraviolet radiation. They exhibit anunfortunate tendency to decompose more or less rapidly under the actionof the latter. Thus, this photochemical sensitivity of dibenzoylmethanederivatives in the face of the ultraviolet radiation to which they areby nature intended to be subjected does not make it possible toguarantee constant protection during prolonged exposure to the sun, sothat the user is subjected to the restriction of having to make repeatedapplications at regular and frequent intervals of time in order toobtain effective protection of the skin against UV radiation. The sameapplies for cinnamic acid derivatives.

Consequently, attempts have been made to reduce the sensitivity to UVradiation of these screening agents (denoted in the continuation of thepresent document by photosensitive screening agents) but numerousformulating problems have been encountered. For example, a specificphotosensitive screening agent may not be able to be formulated withsome other active products, requiring on each occasion the developmentof a new formulation. Likewise, a photosensitive screening agent may notbe able to be formulated with some other screening agents, for exampleParsol® 1789 (UV-A screening agent) and Parsol® MCX (UV-B screeningagent). Furthermore, these photosensitive sunscreen agents have aprotective effect which is necessarily limited over time and, in orderto compensate for their sensitivity to UV radiation, it is necessary toinclude large amounts thereof in the formulations without this beingsufficient, however, to solve the problem.

This problem of sensitivity to UV radiation of sunscreen agents is wellknown to the person skilled in the art. In particular, PatentApplication PCT No. WO 98/31333 discloses the incorporation of asunscreen agent in a material prepared by the sol-gel route but thisexhibits the following major disadvantages. The inclusion of thescreening agent in an effective amount in a material such as isdisclosed in this document results in significant incompatibilities asregards stability with respect to UV radiation.

The Applicant Company has found, surprisingly, that, by combining aphotosensitive sunscreen agent with a material prepared by the sol-gelroute comprising at least one silicon alkoxide and at least onesurfactant, a material is obtained which has an improved stability withrespect to UV radiation. The photostable material and the cosmeticand/or dermatological compositions which comprise an effective amount ofthis material are able to form films with a pleasant feel and exhibitvery good persistence toward pure or salt water and toward polar andnonpolar cosmetic oils.

A subject matter of the present invention is thus a process forimproving the stability with respect to UV radiation of a photosensitivescreening agent which comprises the incorporation of the screening agentin a material prepared by the sol-gel route from at least one siliconalkoxide and from at least one surfactant.

Another subject matter is a photostable material comprising aphotosensitive screening agent combined with a photostabilizing materialprepared by the sol-gel route from at least one silicon alkoxide andfrom at least one surfactant.

Another subject matter of the present invention is a cosmetic and/ordermatological composition comprising an effective amount of aphotostable material according to the invention.

Other characteristics, aspects and advantages of the invention willbecome even more clearly apparent on reading the description and variousexamples which follow.

According to the present invention, the process for improving thestability with respect to UV radiation of a photosensitive sunscreenagent comprises the incorporation of said screening agent in a materialprepared by the sol-gel route including:

(a) at least one silicon alkoxide chosen from those corresponding to oneof the following formulae:

Si(OR₁)₄  (I)

R—Si(OR₁)₃  (II)

 (R₁O)₃—Si—R″—Si(OR₁)₃  (III)

in which:

R₁ represents a linear or branched C₁₋₃₀, preferably C₁₋₆, alkyl group;

R and R′, independently of one another, represent a linear or branchedalkyl group, a cycloalkyl group or an aryl group which is substituted orunsubstituted, it being possible for said R and R′ groups toadditionally comprise a cosmetically or dermatologically active group;R>> represents a linear or branched alkylene group, a cycloalkylenegroup or an arylene group which is substituted or unsubstituted, itbeing possible for said R>> group to additionally comprise acosmetically or dermatologically active group;

(b) at least one solvent,

(c) at least one surfactant, and

(d) water.

Mention may be made, among the cosmetically or dermatologically activegroups which can be carried by the R, R′ and R>> groups, of, forexample, a coloring group, a photochromic group, a group which promotesadhesion to keratinous substances, such as groups of phosphate,phosphonate, phosphonic acid, amide, urethane, ureido, hydroxyl,carboxyl, thiol, amino acid or polypeptide type, a group for combatingfree radicals or a vitamin-carrying group.

Preference is very particularly given, among the silicon alkoxidesdefined above, to tetraethoxysilane and methyltriethoxysilane.

The surfactants which can be used in the present invention are all thecompounds which are chemically compatible with the silicon alkoxide, thesolvent and the photosensitive sunscreen agent.

The surfactant is preferably a nonionic surfactant generally chosen frompolyethoxylated, polypropoxylated or polyglycerolated fatty alcohols,alkylphenols or acids with a fatty chain comprising from 6 to 32 carbonatoms, preferably from 8 to 18 carbon atoms, the number of ethyleneoxide or propylene oxide groups being between 2 and 100, preferablybetween 2 and 50, and the number of glycerol groups being between 2 and30.

Mention may also be made, as nonionic surfactant, of copolymers ofethylene oxide and of propylene oxide; condensates of ethylene oxide andof propylene oxide with fatty alcohols; polyethoxylated fatty amidespreferably having 2 to 30 mol of ethylene oxide; polyglycerolated fattyamides preferably comprising 1 to 5 glycerol groups and in particular1.5 to 4; polyethoxylated fatty amines preferably having 2 to 30 mol ofethylene oxide; sorbitan fatty acid esters ethoxylated with 2 to 30 molof ethylene oxide; sucrose fatty acid esters, polyethylene glycol fattyacid esters, alkylpolyglucosides, carbamate or amide derivatives ofN-alkylglucamines, aldobionamides or amine oxides, such as alkylamine orN-(acylamidopropyl)morpholine oxides.

Preference is very particularly given, among the surfactants mentionedabove, to the use of a polyethoxylated4-(1,1,3,3-tetramethylbutyl)phenol. The latter is sold under the name ofTriton® X100 by Rohm & Haas.

The amount of surfactant used in the present invention will depend onits solubility in the alkoxide/solvent/water mixture. The ratio byweight of the surfactant to the silicon alkoxide generally varies from0.01% to 99%, preferably from 1% to 60%.

Mention may be made, among photosensitive sunscreen agents which can beused according to the invention, of dibenzoylmethane derivatives andcinnamic acid derivatives. Mention may be made, among dibenzoylmethanederivatives, without being restricted thereto, of:

2-methyldibenzoylmethane,

4-methyldibenzoylmethane,

4-isopropyldibenzoylmethane,

4-tert-butyldibenzoylmethane,

2,4-dimethyldibenzoylmethane,

2,5-dimethyldibenzoylmethane,

4,4′-diisopropyldibenzoylmethane,

4,4′-dimethoxydibenzoylmethane,

4-tert-butyl-4′-methoxydibenzoylmethane,

2-methyl-5-isopropyl-4′-methoxydibenzoylmethane,

2-methyl-5-tert-butyl-4′-methoxydibenzoylmethane,

2,4-dimethyl-4′-methoxydibenzoylmethane,

2,6-dimethyl-4-tert-butyl-4′-methoxydibenzoylmethane.

Preference is very particularly given, among the dibenzoylmethanederivatives mentioned above, according to the present invention, to4-tert-butyl-4′-methoxydibenzoylmethane, available commercially underthe name Parsol® 1789 from Hoffmann-Laroche.

Use may be made, as other photosensitive screening agent, of cinnamicacid derivatives chosen from those corresponding to the followinggeneral formula:

in which:

A represents:

an OR³ group, R³ being chosen from a hydrogen atom, a phytyl or benzylgroup, a saturated or unsaturated and linear, branched or cyclic C₁-C₁₈alkyl group, an alkali metal or an alkaline earth metal salt [sic] or anammonium ion [sic], or

an NHR⁴ group, R⁴ being chosen from a hydrogen atom, a phytyl or benzylgroup or a saturated or unsaturated and linear, branched or cyclic C₁-₁₈alkyl group;

R¹ represents a group chosen from H, OH, C₁-C₆ alkoxy, preferablymethoxy, or a saturated or unsaturated and linear, branched or cyclicC₁-C₁₈ alkyl group;

R² represents a group chosen from H, OH or C₁-C₆ alkoxy, preferablymethoxy.

The photosensitive screening agent from this family is preferably2-ethylhexyl p-cinnamate, which is available commercially under the nameof <<Parsol® MCX>> from Hoffmann-Laroche.

The photosensitive sunscreen agent is present in the sol in an amountranging from 0.1% by weight up to its solubility limit in the sol, thepercentage being expressed with respect to the weight of the siliconalkoxide. The photosensitive sunscreen agent is preferably present in anamount ranging from 0.1% by weight to 10% by weight with respect to theweight of the silicon alkoxide.

The solvent which is used in the present invention is preferably alinear or branched lower alcohol, better still ethanol.

The amount of solvent used in the present invention varies from 1% byweight to 85% by weight with respect to the weight of the sol.

Finally, the amount of water used in the material must be sufficient toproduce complete or partial hydrolysis of the silicon alkoxide.

The pH of the water of the hydrolysis preferably lies within the rangefrom 1 to 4, better still within the range from 1 to 2.

The present invention also relates to a photostable material comprisinga photosensitive sunscreen agent combined with a photostabilizingmaterial prepared by the sol-gel route including:

(a) at least one silicon alkoxide,

(b) at least one solvent,

(c) at least one nonionic surfactant, and

(d) water.

The term <<photostable material>> is understood to mean a materialexhibiting an improved stability with respect to UV radiation.

All the (a), (b) and (d) constituents and the photosensitive sunscreenagent of the photostable material are as described above.

The nonionic surfactants which are suitable in the photostable materialaccording to the present invention are chosen in particular frompolyethoxylated, polypropoxylated or polyglycerolated fatty alcohols,alkylphenols or acids with a fatty chain comprising from 6 to 32 carbonatoms, preferably from 8 to 18 carbon atoms, the number of ethyleneoxide or propylene oxide groups being between 2 and 100, preferablybetween 2 and 50, and the number of glycerol groups being between 2 and30.

Mention may also be made, as nonionic surfactants, of copolymers ofethylene oxide and of propylene oxide; condensates of ethylene oxide andof propylene oxide with fatty alcohols; polyethoxylated fatty amidespreferably having 2 to 30 mol of ethylene oxide; polyglycerolated fattyamides preferably comprising 1 to 5 glycerol groups and in particular1.5 to 4; polyethoxylated fatty amines preferably having 2 to 30 mol ofethylene oxide; sorbitan fatty acid esters ethoxylated with 2 to 30 molof ethylene oxide; sucrose fatty acid esters, polyethylene glycol fattyacid esters, alkylpolyglucosides, carbamate or amide derivatives ofN-alkylglucamines, aldobionamides or amine oxides, such as alkylamine orN-(acylamidopropyl)morpholine oxides.

Preference is very particularly given, among the surfactants mentionedabove, to the use of a polyethoxylated4-(1,1,3,3-tetramethylbutyl)phenol. The latter is sold under the name ofTriton® X100 by Rohm & Haas.

In order to preferably obtain the best photostabilizing effect, theconstituents of the photostable material according to the invention areadded in the following way. The silicon alkoxide is added to a solventand then the following are added in the order shown below:

(1) the nonionic surfactant,

(2) the photosensitive sunscreen agent and

(3) the water.

The photostable material thus obtained can be dried and milled, andagain brought into contact with another silicon alkoxide and/or asolvent and water to carry out a surface treatment of the powder. Anadditional layer is then obtained which further improves the stabilitywith respect to UV radiation.

An additional subject matter of the present invention is a cosmeticand/or dermatological composition comprising, in a cosmetically and/ordermatologically acceptable vehicle, an effective amount of aphotostable material according to the invention.

This cosmetic and/or dermatological composition comprises thephotostable material according to the invention in an effective amountranging from 1% by weight to 99% by weight, preferably from 1% by weightto 60% by weight, with respect to the total weight of the composition.

The cosmetic and/or dermatological composition can be provided in theform of a sol which is able to form a film and which can be applieddirectly to the skin to protect it against ultraviolet radiation. Thisapplication can be carried out, for example, by means of a spray.

The photostable material according to the invention is preferably driedand milled, and added in the form of particles to a cosmetic and/ordermatological composition. The mean size of the particles obtainedafter drying and milling the photostable material lies within the rangefrom 0.1 to 50 μm, preferably from 0.1 to 20 μm, better still from 0.1to 10 μm.

The cosmetic and/or dermatological compositions targeted by the presentinvention can, of course, comprise one or more additional sunscreenagents which are active in the UV-A region and/or UV-B region other thanthe photosensitive sunscreen agents defined above, these additionalsunscreen agents being water soluble, fat soluble or insoluble in thecosmetic solvents commonly used. These additional screening agents canbe chosen in particular from salicylic derivatives, camphor derivatives,triazine derivatives, such as those disclosed in Patent ApplicationsU.S. Pat. No. 4,367,390, EP 0 863 145, EP 0 517 104, EP 0 570 838, EP 0796 851, EP 0 775 698, EP 0 878 469, EP 0 933 376 and EP 0 893 119,benzophenone derivatives, β,β′-diphenylacrylate derivatives,benzimidazole derivatives, methylenebis(hydroxyphenylbenzotriazole)derivatives, such as those disclosed in Patent Applications U.S. Pat.No. 5,237,071, U.S. Pat. No. 5,166,355, GB 2 303 549, DE 19726184 and EP0 893 119, p-aminobenzoic acid derivatives, the screeninghydrocarbonaceous and screening silicone polymers disclosed inApplication WO-93/04665, and bis(benzoazolyl) derivatives, such as thosedisclosed in Patent Application [sic] EP 0 669 323 and U.S. Pat. No.2,463,264.

Mention may be made, as examples of additional sunscreen agents whichare active in the UV-A region and/or the UV-B region, of:

p-aminobenzoic acid,

ethoxylated (25 mol) p-aminobenzoate,

2-ethylhexyl p-dimethylaminobenzoate,

N-propoxylated ethyl p-aminobenzoate,

glycerol p-aminobenzoate,

homomenthyl salicylate,

2-ethylhexyl salicylate,

triethanolamine salicylate,

4-isopropylbenzyl salicylate,

menthyl anthranilate,

2-ethylhexyl 2-cyano-3,3-diphenylacrylate,

ethyl 2-cyano-3,3-diphenylacrylate,

2-phenylbenzimidazole-5-sulfonic acid and its salts,

3-((4′-trimethylammonium)benzylidene)bornan-2-one [sic] methyl sulfate,

2-hydroxy-4-methoxybenzophenone,

2-hydroxy-4-methoxybenzophenone-5-sulfonate [sic],

2,4-dihydroxybenzophenone,

2,40,4,4′-tetrahydroxybenzophenone,

2,2′-dihydroxy-4,4′-dimethoxybenzophenone,

2-hydroxy-4-(n-octoxy)benzophenone,

2-hydroxy-4-methoxy-4′-methylbenzophenone,

α-(2-oxoborn-3-ylidene)tolyl-4-sulfonic [sic] acid and its salts,

3-((4′-sulfo)benzylidene)bornan-2-one [sic] and its salts,

3-(4′-methylbenzylidene)-d,l-camphor,

3-benzylidene-d,l-camphor,

urocanic acid,

2,4,6-tris[p-(2′-ethylhexyl-1′-oxycarbonyl)anilino]-1,3,5-triazine,

2-[(p-(tert-butylamido)anilino]-4,6-bis[(p-(40-ethylhexyl-1′-oxycarbonyl)anilino]-1,3,5-triazine[sic],

2,4-bis{[4-(2-ethylhexyloxy)-2-hydroxy]phenyl}-6-(4-methoxyphenyl)-1,3,5-triazine[sic] (Tinosorb®, Ciba-Geigy),

the polymer of N-(2- and4-)[(2-oxoborn-3-ylidene)-methyl)benzyl]acrylamide,

1,4-bis(benzimidazolyl)phenylene-3,31,5,51-tetra-sulfonic acid and itssoluble salts,

polyorganosiloxanes comprising a benzalmalonate functional group,

polyorganosiloxanes comprising a benzotriazole function, such asdrometrizole trisiloxane,

[2,2′-methylenebis[6-(2H-benzotriazol-2-yl)-4-(1,1,3,3-tetramethylbutyl)phenol][sic] in the dissolved form, such as the product sold under the nameMixxim® BB/100 by Fairmount Chemical, or else in insoluble micronizedform, such as the product sold under the name Tinosorb® M by Ciba-Geigy,

[2,2′-methylenebis[6-(2H-benzotriazol-2-yl)-4-(methyl)phenol] [sic] inthe dissolved form, such as the product sold under the name Mixxim®BB/200 by Fairmount Chemical.

The compositions according to the invention can also comprise agents forthe artificial tanning and/or browning of the skin (self-tanningagents), such as, for example, dihydroxyacetone (DHA).

The cosmetic and/or dermatological compositions according to theinvention can also comprise pigments or alternatively nanopigments (meansize of the primary particles, in general between 5 nm and 100 nm,preferably between 10 and 50 nm) formed of coated or uncoated metaloxides, such as, for example, nanopigments formed of titanium oxide(amorphous or crystalline in the rutile and/or anatase form), ironoxide, zinc oxide, zirconium oxide or cerium oxide which are allphotoprotective agents well known per se which act by physical blocking(reflection and/or scattering) of UV radiation. Conventional coatingagents are, furthermore, alumina and/or aluminum stearate. Suchnanopigments formed of coated or uncoated metal oxides are disclosed inparticular in Patent Applications EP-A-0 518 772 and EP-A-0 518 773.

The compositions in accordance with the present invention canadditionally comprise conventional cosmetic adjuvants chosen inparticular from fatty substances, organic solvents, ionic or nonionicthickeners, softeners, antioxidants, agents for combating free radicals,opacifiers, stabilizers, emollients, silicones, (α-hydroxy acids,antifoaming agents, moisturizing agents, vitamins, fragrances,preservatives, surfactants, fillers, sequestering agents, polymers,propellants, basifying or acidifying agents, dyes or any otheringredient commonly used in the cosmetics and/or dermatological field,in particular for the manufacture of antisun compositions in the form ofemulsions.

The fatty substances can be composed of an oil or a wax or theirmixtures. The term <<oil>> is understood to mean a compound which isliquid at ambient temperature. The term <<wax>> is understood to mean acompound which is solid or substantially solid at ambient temperatureand which has a melting point generally of greater than 350° C.

Mention may be made, as oils, of mineral oils (liquid petrolatum);vegetable oils (sweet almond, macadamia, blackcurrant seed or jojobaoil); synthetic oils, such as perhydrosqualene, fatty alcohols, acids oresters (such as the benzoate C₁₂-C₁₅ alcohols sold under the name<<Finsolv TN>> by Finetex, octyl palmitate, isopropyl lanolate ortriglycerides, including those of capric/caprylic acids), or ethoxylatedor propoxylated fatty esters and ethers; silicone oils (cyclomethicone,preferably comprising 4 or 5 silicon atoms, or polydimethylsiloxane orPDMS); fluorinated oils; or polyalkylenes.

Mention may be made, as waxy compounds, of paraffin wax, carnauba wax,beeswax or hydrogenated castor oil.

Mention may be made, among organic solvents, of lower alcohols andpolyols.

The thickeners can be chosen in particular from crosslinked polyacrylicacids, modified or unmodified guar and cellulose gums, such ashydroxypropylated guar gum, methylhydroxyethylcellulose orhydroxypropylmethylcellulose, and silicone gums, such as, for example, apolydimethylsiloxane derivative.

The cosmetic and/or dermatological compositions according to theinvention can be prepared according to techniques well known to a personskilled in the art, in particular those intended for the preparation ofemulsions of oil-in-water or water-in-oil type.

This cosmetic and/or dermatological composition can be provided inparticular in the form of a simple or complex emulsion (O/W, W/O, O/W/Oor W/O/W), such as a cream or a milk, or in the form of a gel or a creamgel, of a powder or of a solid stick and can optionally be packaged inan aerosol and be provided in the form of a foam or a spray.

The cosmetic and/or dermatological compositions according to theinvention are preferably provided in the form of an oil-in-wateremulsion.

When it is an emulsion, the aqueous phase of the latter can comprise anonionic vesicular dispersion prepared according to known processes(Bangham, Standish and Watkins, J. Mol. Biol., 13, 238 (1965), FR 2 315991 and FR 2 416 008).

The cosmetic and/or dermatological composition according to theinvention is used as composition for protecting the skin or keratinoussubstances against ultraviolet rays, as antisun composition or as makeupproduct.

When the cosmetic composition according to the invention is used forprotecting the hair, it can be provided in the form of a shampoo,lotion, gel, emulsion or nonionic vesicular dispersion and canconstitute, for example, a rinse-out composition, to be applied beforeor after shampooing, before or after dyeing or bleaching or before,during or after perming or hair straightening, a styling or treatinglotion or gel, a lotion or a gel for blow drying or hairsetting, or acomposition for perming or straightening or for dyeing or bleaching thehair.

The examples are given by way of illustration in the present inventionand are not understood in any way to be limiting.

EXAMPLE 1

A material is synthesized by the sol-gel route from:

Tetraethoxysilane (TEOS) 1.8 g Absolute ethanol 13.6 g Water (0.01N HCl)1.0 g Triton ® X-100 0.6 g Parsol ® 1789 0.04 g

the tetraethoxysilane originating from Fluka, the Parsol® 1789 beingsold by Hoffmann-Laroche and the Triton® X-100 being sold by Rohm &Haas.

The TEOS is added to the ethanol with stirring. The Triton® X-100 issubsequently added with stirring, followed by the Parsol® 1789, stillwith stirring. No incompatibility between the components was observed.The mixture is stirred for 5 minutes. The water (0.01N HCl) is added andthe mixture is stirred for 60 minutes at 30° C. The mixture is allowedto return to ambient temperature with stirring. The material is readyfor use.

EXAMPLE 2

A material is synthesized by the sol-gel route from:

Tetraethoxysilane (TEOS) 1.8 g Absolute ethanol 14.43 g Water (0.1N HCl)1.5 g Triton ® X-100 0.6 g Parsol ® 1789 0.05 g Methyltriethoxysilane(MTES) 3.2 g

the tetraethoxysilane originating from Fluka, the Parsol® 1789 beingsold by Hoffmann-Laroche, the Triton® X-100 being sold by Rohm & Haasand the methyltriethoxysilane being sold by Interchim.

The TEOS is added to the ethanol with stirring. The Triton® X-100 issubsequently added with stirring, followed by the Parsol® 1789, stillwith stirring. The mixture is stirred for 5 minutes. Water (0.01N HCl)is added and the mixture is stirred for 30 minutes at 48° C. The mixtureis allowed to return to ambient temperature with stirring. The sol thusobtained is placed in a ventilated oven at 50° C. for 24 hours. A whitesolid is then obtained, which solid is milled in order to obtain a whitepowder.

Furthermore, a sol is prepared from the MTES. For this, the MTES, theethanol and the water are mixed at ambient temperature and the mixtureis stirred for 1 hour at ambient temperature. Subsequently, 500 mg ofthe powder obtained above are dissolved in this sol prepared from MTES.This novel sol comprising powder is ready for use.

Tests of Stability with Respect to UV Radiation

Tests of stability with respect to UV radiation of Parsol® 1789 weresubsequently carried out by irradiating the materials obtained inExamples 1 and 2 and, by way of comparison, materials comprising Parsol®1789 but without surfactant.

The materials are deposited on glass sheets (microscope slides). Filmsare formed on the sheets after evaporation of the volatile components ofthe mixture. The drying time of the films is fast, that is to saybetween 1 and 3 minutes.

The films obtained are then irradiated under the following conditions:

Energy of the UV-A lamp=19 mW/cm²,

Energy of the UV-B lamp=0.6 mW/cm²,

Irradiation time=20 minutes.

These conditions correspond to approximately 1 hour of sunshine.

The photodecomposition is monitored by absorption spectrophotometry orby HPLC. The results are combined in the following table.

TABLE Photodecomposition Film after irradiating Materials studiedformation for 20 minutes TEOS no — MTES/TEOS yes 70% 40/60 (in mol) MTMSyes 55% TEOS/3.7% yes 25% (±2%) Triton ® X-100 (Example 1) TEOS/3.7% yes20% (±2%) Triton ® X-100/MTES (Example 2) MTMS: methyltrimethoxysilane.

From this table, the materials according to the present inventionexhibit better stability with respect to UV radiation in comparison withthe materials not comprising surfactant. Furthermore, all the materialsstudied were observed to be persistent toward pure or salt water andtoward polar and nonpolar cosmetic oils.

What is claimed is:
 1. A process for improving the stability withrespect to UV radiation of a photosensitive sunscreen agent, wherein theprocess comprises the incorporation of said sunscreen agent in aphotostabilizing material prepared by sol-gel route from at least onesilicon alkoxide and at least one non-ionic surfactant.
 2. The processof claim 1, wherein the photostabilizing material prepared by thesol-gel route comprises at least one silicon alkoxide, at least onesurfactant, at least one solvent and water.
 3. The process of claim 1,wherein the silicon alkoxide has a formula corresponding to one of thefollowing formulae: Si(OR₁)₄  (I) R—Si(OR₁)₃  (II)(R₁O)₃—Si—R″—Si(OR₁)₃  (III)

wherein: R₁ represents a linear or branched C₁₋₃₀, alkyl group; R andR′, independently of one another, represent a linear or branched alkylgroup, a cycloalkyl group or an aryl group which is substituted orunsubstituted; R″ represents a linear or branched alkylene group, acycloalkylene group or an arylene group which is substituted orunsubstituted.
 4. The process of claim 3, wherein R₁ is linear orbranched C₁₋₆ alkyl group.
 5. The process of claim 3, wherein R, R′and/or R″ further comprises a cosmetically or dermatologically activegroup.
 6. The process of claim 1, wherein the silicon alkoxide isselected from the group consisting of tetraethoxysilane andmethyltriethoxysilane.
 7. The process of claim 1, wherein the nonionicsurfactant is selected from the group consisting of polyethoxylated,polypropoxylated and polyglycerolated fatty alcohols, alkylphenols andacids with a fatty chain comprising from 6 to 32 carbon atoms, thenumber of ethylene oxide or propylene oxide groups being between 2 and100 and the number of glycerol groups being between 2 and 30; copolymersof ethylene oxide and of propylene oxide; condensates of ethylene oxideand of propylene oxide with fatty alcohols; polyethoxylated fattyamides; polyglycerolated fatty amides; polyethoxylated fatty amines;ethoxylated sorbitan fatty acid esters; sucrose and polyethylene glycolfatty acid esters; alkylpolyglucosides; amide or carbamate derivativesof N-alkylglucamine, aldobionamides and amine oxides.
 8. The process ofclaim 1, wherein the surfactant is a polyethoxylated4-(1,1,3,3-tetramethylbutyl)phenol.
 9. The process of claim 1, whereinthe surfactant is present in an amount from 0.01% to 99% by weight withrespect to the silicon alkoxide.
 10. The process of claim 1, wherein thesurfactant is present in an amount from 10% to 60% by weight withrespect to the silicon alkoxide.
 11. The process of claim 1, wherein thephotosensitive sunscreen agent is selected from the group consisting ofdibenzoylmethane derivatives and cinnamic acid derivatives.
 12. Theprocess of claim 1, wherein the photosensitive sunscreen agent isselected from the group consisting of: 2-methyldibenzoylmethane,4-methyldibenzoylmethane, 4-isopropyldibenzoylmethane,4-tert-butyldibenzoylmethane, 2,4-dimethyldibenzoylmethane,2,5-dimethyldibenzoylmethane, 4,4′-diisopropyldibenzoylmethane,4,4′-dimethoxydibenzoylmethane, 4-tert-butyl-4′-methoxydibenzoylmethane,2-methyl-5-isopropyl-4′-methoxydibenzoylmethane,2-methyl-5-tert-butyl-4′-methoxydibenzoylmethane,2,4-dimethyl-4′-methoxydibenzoylmethane, and2,6-dimethyl-4-tert-butyl-4′-methoxydibenzoylmethane.
 13. The process ofclaim 1, wherein the photosensitive sunscreen agent is4-tert-butyl-4′-methoxydibenzoylmethane.
 14. The process of claim 1,wherein the photosensitive sunscreen agent is chosen from cinnamic acidderivatives corresponding to the following general formula: wherein Arepresents:

an OR³ group, R³ being selected from the group consisting hydrogen atom,a phytyl or benzyl group, a saturated or unsaturated and linear,branched or cyclic C₁-C₁₈ alkyl group, an alkali metal or an alkalineearth metal salt or an ammonium ion, or an NHR⁴ group, wherein R⁴ is ahydrogen atom, a phytyl or benzyl group or a saturated or unsaturated,linear, branched or cyclic C₁-C₁₈ alkyl group; R¹ represents a groupselected from the group consisting of H, OH, C₁-C₆ alkoxy, andsaturated, unsaturated, linear, branched and cyclic C₁-C₁₈ alkyl groups;R² represents a group chosen from H, OH or C₁-C₆ alkoxy.
 15. The processof claim 14, wherein R1 and/or R2 are methoxy.
 16. The process of claim14, wherein the photosensitive sunscreen agent is 2-ethylhexylp-cinnamate.
 17. The process of claim 1, wherein the photosensitivesunscreen agent is present in an amount ranging from 0.1% by weight upto its solubility limit in sol with respect to the weight of the siliconalkoxide.
 18. The process of claim 1, wherein the photosensitivesunscreen agent is present in an amount ranging from 0.1% by weight to10% by weight with respect to the total weight of the silicon alkoxide.19. The process of claim 2, wherein the solvent is an alcohol.
 20. Theprocess of claim 19, wherein the alcohol is a linear or branched loweralcohol.
 21. The process of claim 20, wherein the alcohol is ethanol.22. The process of claim 2, wherein the solvent is present in an amountfrom 1 to 85% by weight with respect to the total weight of thematerial.
 23. The process of claim 1, wherein the sol gel routecomprises hydrolysis conducted in water corresponding to a pH of from 1to
 4. 24. The process of claim 23, wherein the hydrolysis is conductedin water corresponding to a pH of from 1 to
 2. 25. A photostablematerial comprising a photosensitive sunscreen agent combined with aphotostabilizing material prepared by sol-gel route and comprising: (a)at least one silicon alkoxide, (b) at least one solvent, (c) at leastone nonionic surfactant, and (d) water.
 26. The photostable material ofclaim 25, wherein the silicon alkoxide has a formula corresponding toone of the following formulae: Si(OR₁)₄  (I) R—Si(OR₁)₃  (II)(R₁O)₃—Si—R″—Si(OR₁)₃  (III)

wherein: R₁ represents a linear or branched C₁₋₃₀, alkyl group; R andR′, independently of one another, represent a linear or branched alkylgroup, a cycloalkyl group or an aryl group which is substituted orunsubstituted; R″ represents a linear or branched alkylene group, acycloalkylene group or an arylene group which is substituted orunsubstituted.
 27. The photostable material of claim 26, wherein R₁ islinear or branched C₁₋₆ alkyl group.
 28. The photostable material ofclaim 26, wherein R, R′ and/or R″ further comprises a cosmetically ordermatologically active group.
 29. The photostable material of claim 25,wherein the silicon alkoxide is selected from the group consisting oftetraethoxysilane and methyltriethoxysilane.
 30. The photostablematerial of claim 25, wherein the surfactant is a nonionic surfactant.31. The photostable material of claim 30, wherein the nonionicsurfactant is selected from the group consisting of polyethoxylated,polypropoxylated and polyglycerolated fatty alcohols, alkylphenols andacids with a fatty chain comprising from 6 to 32 carbon atoms, thenumber of ethylene oxide or propylene oxide groups being between 2 and100 and the number of glycerol groups being between 2 and 30; copolymersof ethylene oxide and of propylene oxide; condensates of ethylene oxideand of propylene oxide with fatty alcohols; polyethoxylated fattyamides; polyglycerolated fatty amides; polyethoxylated fatty amines;ethoxylated sorbitan fatty acid esters; sucrose and polyethylene glycolfatty acid esters; alkylpolyglucosides; amide or carbamate derivativesof N-alkylglucamine, aldobionamides and amine oxides.
 32. Thephotostable material of claim 25, wherein the surfactant is apolyethoxylated 4-(1,1,3,3-tetramethylbutyl)phenol.
 33. The photostablematerial of claim 25, wherein the photosensitive sunscreen agent isselected from the group consisting of dibenzoylmethane derivatives andcinnamic acid derivatives.
 34. The photostable material of claim 25,wherein the photosensitive sunscreen agent is selected from the groupconsisting of: 2-methyldibenzoylmethane, 4-methyldibenzoylmethane,4-isopropyldibenzoylmethane, 4-tert-butyldibenzoylmethane,2,4-dimethyldibenzoylmethane, 2,5-dimethyldibenzoylmethane,4,4′-diisopropyldibenzoylmethane, 4,4′-dimethoxydibenzoylmethane,4-tert-butyl-4′-methoxydibenzoylmethane,2-methyl-5-isopropyl-4′-methoxydibenzoylmethane,2-methyl-5-tert-butyl-4′-methoxydibenzoylmethane,2,4-dimethyl-4′-methoxydibenzoylmethane, and2,6-dimethyl-4-tert-butyl-4′-methoxydibenzoylmethane.
 35. Thephotostable material of claim 25, wherein the photosensitive sunscreenagent is 4-tert-butyl-4′-methoxydibenzoylmethane.
 36. The photostablematerial of claim 25, wherein the photosensitive sunscreen agent ischosen from cinnamic acid derivatives corresponding to the followinggeneral formula:

wherein A represents: an OR³ group, R³ being selected from the groupconsisting hydrogen atom, a phytyl or benzyl group, a saturated orunsaturated and linear, branched or cyclic C₁-C₁₈ alkyl group, an alkalimetal or an alkaline earth metal salt or an ammonium ion, or an NHR⁴group, wherein R⁴ is a hydrogen atom, a phytyl or benzyl group or asaturated or unsaturated, linear, branched or cyclic C₁-C₁₈ alkyl group;R¹ represents a group selected from the group consisting of H, OH, C₁-C₆alkoxy, and saturated, unsaturated, linear, branched and cyclic C₁-C₁₈alkyl groups; R² represents a group chosen from H, OH or C₁-C₆ alkoxy,preferably methoxy.
 37. The photostable material of claim 36, wherein R1and/or R2 are methoxy.
 38. The photostable material of claim 25, whereinthe photosensitive sunscreen agent is 2-ethylhexyl p-cinnamate.
 39. Thephotostable material of claim 25, wherein the solvent is an alcohol. 40.The photostable material of claim 39, wherein the alcohol is a linear orbranched lower alcohol.
 41. The photostable material of claim 40,wherein the alcohol is ethanol.
 42. The photostable material of claim25, wherein the silicon alkoxide is added to a solvent and then, in thefollowing order, the nonionic surfactant, the photosensitive sunscreenagent and the water are added.
 43. The photostable material of claim 42,wherein the material is dried and milled, and brought into contact withanother silicon alkoxide and/or a solvent and water.
 44. A cosmeticand/or dermatological composition comprising a screening agent which isphotosensitiveto UV radiation and an effective amount of the photostablematerial of claim 25 in cosmetically and/or dermatologically acceptablevehicle.
 45. The cosmetic and/or dermatological composition of claim 44,further comprising an additive selected from the group consisting ofsunscreen agents other than photosensitive sunscreen agents, agents forthe artificial tanning and/or browning of the skin, pigments, fattysubstances, organic solvents, thickeners, softeners and antioxidants.46. The cosmetic and/or dermatological composition of claim 44, whereinthe photostable material is added in an effective amount ranging from 1%by weight to 99% by weight, with respect to the total weight of thecosmetic and/or dermatological composition.
 47. The cosmetic and/ordermatological composition of claim 44, wherein the photostable materialis added in an effective amount ranging from 10% by weight to 60% byweight, with respect to the total weight of the cosmetic and/ordermatological composition.
 48. The cosmetic and/or dermatologicalcomposition of claim 44, wherein the photostable material is in the formof particles obtained by drying and milling.
 49. The cosmetic and/ordermatological composition of claim 48, wherein the mean size of theparticles obtained by drying and milling the photostable material isfrom 0.1 to 50 μm.
 50. The cosmetic and/or dermatological composition ofclaim 48, wherein the mean size of the particles obtained by drying andmilling the photostable material is from 0.1 to 20 μm.